Document EP 2226277 B1 discloses a rotary conveyor for transferring containers comprising a rotor driven by a motor to rotate around rotation axis. The rotor has a perimetric wall having a plurality of suction openings distributed over its periphery in correspondence with retention elements configured to engage the containers. In a region inside the perimetric wall of the rotor there is a stationary suction chamber connected to a low pressure source. The suction chamber defines a laterally open channel facing the perimetric wall along a predetermined arc of circumference, so that the suction chamber is delimited in part by the perimetric wall of the rotor so that when the rotor rotates the suction openings communicate directly with the suction chamber along the predetermined arc of circumference. As the rotor rotates, a container is held by suction in each of the retention elements at the start of the predetermined arc of circumference, is carried by the rotor along the predetermined arc of circumference, and is released at the end of the predetermined arc of circumference.
Document EP 2722296 A1 discloses a rotary conveyor with change of pitch for transferring containers, comprising a rotary platform rotating about a rotation axis, a plurality of guide elements fixed to the rotary platform and a plurality of slots parallel to the guide elements formed in the rotary platform. The guide elements and the slots are uniformly distributed around the rotation axis and extend from a peripheral region to a central region of the rotary platform. A stationary closed-loop cam defining a path not centered with respect to the rotation axis is located below the rotary platform. Each guide element has coupled thereto a slide provided with a cam follower inserted through the corresponding slot and coupled to the closed-loop cam, such that each slide performs a back and forth movement along the corresponding guide element during one rotation of the rotary platform.
In the rotary conveyor of the mentioned document EP 2722296 A1, each slide has fixed thereto a retention element provided with a suction port suitable for retaining a container, and each suction port is in communication with a suction chamber through a corresponding suction conduit. The suction chamber is located in a stationary position below the rotary platform and has an upper wall in contact with a lower surface of the rotary platform. The closed-loop cam and a suction slot parallel to a portion of the path defined by the closed-loop cam are formed in this upper wall of the suction chamber. The suction conduit of each slide has an open lower end which communicates with the suction chamber through an intersection of the corresponding slot formed in the rotary platform and the suction slot formed in the suction chamber, and this open lower end of the suction conduit follows the changing position of the mentioned intersection during the back and forth movement of the slide during a part of each rotation of the rotary platform.
The rotary conveyor of the mentioned document EP 2722296 A1 has several drawbacks. First, the fact that the upper wall of the suction chamber is in contact with a lower surface of the rotary platform can generate considerable friction resulting in unacceptable component wear and/or heating. Furthermore, the fact that both the closed-loop cam and the suction slot are formed in the upper wall of the suction chamber makes it necessary to replace the entire suction chamber when only the path of the closed-loop cam is to be modified. On the other hand, the fact of using the slots formed in the rotary platform both for the passage of the corresponding cam followers and for the passage of air at their intersections with the suction slot requires high precision in the paths of the closed-loop cam, the slots formed in the rotary platform and the suction slot for obtaining an acceptable air flow rate in any position without considerable losses, which imposes certain limitations in the design of such paths.